Fritz,
Thanks for the extra pictures. It would be really interesting if you could look at the breechblock stamps under extreme magnification--an extreme closeup if you can manage it. The two stamps appear to be different, and I am not convinced from this photo that the lower one is e/2.
It appears to be characteristic of Krieghoffs that, more often than not, they do not have witness marks. I've lightened up your photo here to show that; I'm also interested to note the absence of worker's marks or other marks around the recoil lug, so unlike DWM, Efrurt, and Mauser.
I also processed the loading tool and enlarged it a bit. Absent a very magnified view, we will need to depend on your eye to identify it. Are you sure it isn't an e/63?
The "thumbnail", as I am informed, is a patch on the rear part of the frame under the rear toggle, where the toggle tail strikes it at full recoil. It is a small hardened area, heat-treated separately after the frame is completed. It takes blue differently from the steel around it, and looks like a thumbnail-shaped discoloration. It may not photograph easily, although you should see it fairly well.
--Dwight